Nowadays, as electronics are miniaturized and highly integrated, heating density around an exothermic body such as a chip becomes higher and higher, and a thermally conductive sheet having higher thermal conductivity is required. At the same time, a thermally conductive sheet containing a non-silicone resin as a binder component is required because it seldom causes a contact fault in electronics.
As a non-silicone resin sheet or a composition usable in a sheet, there is disclosed, for example, a formed body or a sheet in which a thermally conductive filler is filled in an acrylic resin (see JP-A-2001-310984 and JP-A-2003-238760). There is further disclosed a thermally conductive adhesive containing a (meth)alkyl acrylate monomer and a thermally conductive filler or a thermally conductive adhesive containing a polymerized (meth)alkyl acrylate monomer and a thermally conductive filler (see JP-A-2004-059851 and JP-A-10-316953).
In polyolefin resins, improvement in thermal stability or light stability has variously been tried, and usage of various kinds of thermal stabilizers in systems where a filler such as talc is filled in polyolefin (see Japanese Patent No. 2615829 and Japanese Patent No. 3133375).
However, it is difficult for a (meth)acrylic polymer type thermally conductive sheet as disclosed in the references described above to achieve high thermal conductivity and thermal stability. Particularly, there is a problem that, when the amount of the thermally conductive filler is increased in order to obtain high thermal conductivity, thermal stability is lowered, and the sheet cannot keep flexibility in a certain time period. An olefin resin composition as disclosed in Japanese Patent No. 2615829 or Japanese Patent No. 3133375 has low flexibility and a small amount of thermally conductive filler, which is not suitable for a thermally conductive sheet. Therefore, a non-silicone thermally conductive sheet is required which can have both high thermal conductivity and thermal stability.